RSP Permian (RSPP) 10-Q 2 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 27, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	RSP Permian, Inc.
Entity Central Index Key	1,588,216
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		159,424,148

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
CURRENT ASSETS
Cash and cash equivalents	$ 33,928	$ 38,102
Accounts receivable	128,198	111,157
Derivative instruments	30,186	64
Total current assets	192,312	149,323
PROPERTY, PLANT AND EQUIPMENT
Oil and natural gas properties, successful efforts method	7,049,008	6,802,517
Accumulated depletion	(853,720)	(778,596)
Total oil and natural gas properties, net	6,195,288	6,023,921
Other property and equipment, net	56,308	56,798
Total property, plant and equipment	6,251,596	6,080,719
OTHER LONG-TERM ASSETS
Derivative instruments	4,574	37
Other long-term assets	51,638	40,107
Total other long-term assets	56,212	40,144
TOTAL ASSETS	6,500,120	6,270,186
CURRENT LIABILITIES
Accounts payable	54,209	26,758
Accrued expenses	116,372	119,439
Interest payable	29,604	23,798
Derivative instruments	51,001	36,566
Total current liabilities	251,186	206,561
LONG-TERM LIABILITIES
Derivative instruments	9,321	5,722
Long-term debt	1,579,751	1,509,128
Deferred taxes	232,500	210,568
Other long-term liabilities	16,565	15,849
Total long-term liabilities	1,838,137	1,741,267
Total liabilities	2,089,323	1,947,828
STOCKHOLDERS’ EQUITY
Common stock, $.01 par value; 300,000,000 shares authorized, 159,423,086 shares issued and outstanding at March 31, 2018; 158,596,324 shares issued and outstanding at December 31, 2017	1,594	1,586
Additional paid-in capital	4,127,517	4,128,659
Accumulated earnings	281,686	192,113
Total stockholders’ equity	4,410,797	4,322,358
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 6,500,120	$ 6,270,186

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	159,423,086	158,596,324
Common stock, shares outstanding (in shares)	159,423,086	158,596,324

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
REVENUES
Oil sales	$ 251,977	$ 151,637
Natural gas sales	8,432	7,378
NGLs sales	15,913	10,916
Total revenues	276,322	169,931
OPERATING EXPENSES
Lease operating expenses	32,135	25,411
Production and ad valorem taxes	16,261	9,469
Depreciation, depletion and amortization	76,122	61,040
Asset retirement obligation accretion	205	153
Impairments of oil and natural gas properties	4,200	125
Exploration expenses	246	2,580
General and administrative expenses	14,334	11,712
Merger and acquisition costs	2,757	4,052
Total operating expenses	146,260	114,542
OPERATING INCOME	130,062	55,389
OTHER INCOME (EXPENSE)
Other income, net	1,039	720
Net gain on derivative instruments	2,907	17,121
Interest expense	(22,503)	(19,224)
Total other expense	(18,557)	(1,383)
INCOME BEFORE TAXES	111,505	54,006
INCOME TAX EXPENSE	(21,932)	(15,072)
NET INCOME	$ 89,573	$ 38,934
Earnings per common share:
Basic (in dollars per share)	$ 0.57	$ 0.27
Diluted (in dollars per share)	$ 0.57	$ 0.26
Weighted average shares outstanding:
Basic (in shares)	157,119	146,054
Diluted (in shares)	158,309	147,005

Consolidated Statement of Chang

Consolidated Statement of Changes In Stockholders' Equity - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Earnings (Deficit)
Beginning balance (in shares) at Dec. 31, 2017	158,596,324	158,596,000
Beginning balance at Dec. 31, 2017	$ 4,322,358	$ 1,586	$ 4,128,659	$ 192,113
Stockholders' Equity/Members' Equity [Roll Forward]
Repurchase and retirement of common stock (in shares)		(171,000)
Repurchase and retirement of common stock	(6,461)	$ (2)	(6,459)
Equity-based compensation (in shares)		998,000
Equity-based compensation	5,327	$ 10	5,317
Net income	$ 89,573			89,573
Ending balance (in shares) at Mar. 31, 2018	159,423,086	159,423,000
Ending balance at Mar. 31, 2018	$ 4,410,797	$ 1,594	$ 4,127,517	$ 281,686

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
OPERATING ACTIVITIES:
Net income	$ 89,573	$ 38,934
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	76,122	61,040
Asset retirement obligation accretion	205	153
Impairments of oil and natural gas properties	4,200	125
Equity-based compensation	5,327	3,923
Amortization of loan fees and discount on debt issuance	1,070	1,019
Deferred income taxes	21,932	13,574
Other	(390)	(196)
Net gain on derivative instruments	(2,907)	(17,121)
Net cash payments from settled derivatives	(13,389)	(2,576)
Changes in operating assets and liabilities:
Accounts receivable	(13,693)	(2,250)
Other assets	(11,478)	(9,131)
Accounts payable	27,123	840
Accrued expenses	(11,692)	816
Interest payable	5,806	17,793
Net cash provided by operating activities	177,809	106,943
INVESTING ACTIVITIES:
Development of oil and natural gas properties	(236,590)	(116,830)
Acquisitions of oil and natural gas properties	(8,688)	(598,941)
Acquisition of infrastructure assets	0	(18,828)
Investment in unconsolidated subsidiary	0	(188)
Additions to other property and equipment	244	585
Net cash used in investing activities	(245,522)	(735,372)
FINANCING ACTIVITIES:
Payment of deferred loan costs	0	(491)
Borrowings under long-term debt	70,000	0
Payments of equity issuance costs	0	(80)
Repurchase and retirement of common stock	(6,461)	(7,516)
Net cash provided by (used in) financing activities	63,539	(8,087)
NET CHANGE IN CASH	(4,174)	(636,516)
CASH AT BEGINNING OF PERIOD	38,102	690,776
CASH AT END OF PERIOD	33,928	54,260
SUPPLEMENTAL CASH FLOW INFORMATION
Cash paid for interest	15,627	412
NON-CASH ACTIVITIES
Change in accrued capital expenditures	8,624	(2,175)
Common stock issued for oil and gas properties	0	663,854
Release of deposit held in escrow for oil and gas properties	0	64,122
Asset retirement obligation acquired	$ 0	$ 822

Nature of Operations and Basis

Nature of Operations and Basis of Presentation	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Operations and Basis of Presentation	NATURE OF OPERATIONS AND BASIS OF PRESENTATION Organization and Description of the Business RSP Permian, Inc., a Delaware corporation ("RSP Inc.," the "Company," "we," "our," or "us"), is an independent oil and natural gas company engaged in the acquisition, exploration, exploitation, development and production of unconventional oil and associated liquids-rich natural gas reserves in the Permian Basin of West Texas. The vast majority of the Company’s acreage is located on large, contiguous acreage blocks in the core of the Midland Basin and the Delaware Basin, both sub-basins of the Permian Basin. The Midland Basin properties are primarily in the adjacent counties of Midland, Martin, Andrews, Ector and Glasscock. The Delaware Basin properties are in Loving and Winkler counties. The Company’s common stock is listed and traded on the NYSE under the ticker symbol “RSPP.” Proposed Merger with Concho Resources Inc. On March 27, 2018, we entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Concho Resources Inc., a Delaware corporation (“Concho”), and Green Merger Sub Inc., a Delaware corporation and wholly owned subsidiary of Concho (“Merger Sub”), pursuant to which Merger Sub will merge with and into RSP Inc. (the "Merger"), with RSP Inc. surviving the Merger as a wholly owned subsidiary of Concho. Concho's common stock is listed and traded on the NYSE under the ticker symbol "CXO." The closing of the Merger is expected to occur in the third quarter of 2018. On the terms and subject to the conditions set forth in the Merger Agreement, upon consummation of the Merger, each share of RSP Inc. common stock, par value $0.01 per share, issued and outstanding immediately prior to the effective time of the Merger will be converted into the right to receive from Concho 0.320 of a fully-paid and nonassessable share of common stock, par value $0.001 per share, of Concho (“Concho Shares”). The completion of the Merger is subject to certain customary mutual conditions, including (i) the receipt of the required approvals from the stockholders of RSP Inc. and Concho, (ii) the expiration or termination of the waiting period under the Hart-Scott-Rodino Act, (iii) the absence of any governmental order or law that makes consummation of the Merger illegal or otherwise prohibited, (iv) Concho’s registration statement on Form S-4 having been declared effective by the SEC under the Securities Act of 1933, (v) Concho Shares issuable in connection with the Merger having been authorized for listing on the NYSE, upon official notice of issuance, and (vi) the receipt by each party of a customary opinion that the Merger will qualify as a “reorganization” within the meaning of Section 368(a) of the U.S. tax code. The obligation of each party to consummate the Merger is also conditioned upon the other party’s representations and warranties being true and correct (subject to certain materiality exceptions) and the other party having performed in all material respects its obligations under the Merger Agreement. The Merger Agreement contains termination rights for each of Concho and RSP Inc., including, among others, if the consummation of the Merger does not occur on or before October 31, 2018. Upon termination of the Merger Agreement under specified circumstances, including the termination by RSP Inc. in the event of a change of recommendation by Concho's board of directors, Concho would be required to pay RSP Inc. a termination fee of $350.0 million . Upon termination of the Merger Agreement under specified circumstances, including, generally, the termination by Concho in the event of a change of recommendation by the RSP Inc.'s board of directors or by RSP Inc. to enter into an alternative acquisition agreement, RSP Inc. would be required to pay Concho a termination fee of $250.0 million . On April 20, 2018, Concho filed a registration statement on Form S-4 (the “Form S-4”) to register the Concho Shares to be issued in the Merger. The Form S-4 is subject to review by the SEC, and Concho will file one or more amendments to the Form S-4 in the future. Additional information on the proposed Merger is included in the Form 8-K filed with the SEC on March 28, 2018. Basis of Presentation These consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the SEC and are presented in accordance with generally accepted accounting principles in the United States (“GAAP”). They reflect all adjustments that are, in the opinion of management, necessary for a fair presentation. The consolidated financial statements of the Company include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Certain information, accounting policies, and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States have been omitted pursuant to such rules and regulations, although the Company believes the disclosures are adequate to make the information presented not misleading. The financial statements in this Quarterly Report on Form 10–Q should be read together with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 , which contains a complete summary of the Company’s significant accounting policies and disclosures.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Use of Estimates The preparation of the consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the financial statements and accompanying notes. The more significant estimates pertain to proved oil, natural gas liquids ("NGLs") and natural gas reserves, asset retirement obligations (“AROs”), equity-based compensation, estimates relating to oil, NGLs and natural gas revenues and expenses, accrued liabilities, the fair market value of assets and liabilities acquired in business combinations, derivatives and income taxes. Although management believes these estimates are reasonable, actual results could differ from these estimates. Changes in estimates are recorded prospectively. Significant assumptions are required in the valuation of proved oil, NGLs and natural gas reserves that may affect the amount at which oil and natural gas properties are recorded. Depletion of oil and natural gas properties are determined using estimates of proved oil, NGLs and natural gas reserves. There are numerous uncertainties inherent in the estimation of quantities of proved reserves and in the projection of future rates of production and the timing of development expenditures. Similarly, evaluations for impairment of proved and unproved oil and natural gas properties are subject to numerous uncertainties including, among others, estimates of future recoverable reserves and commodity price estimates. It is possible that these estimates could be revised at future dates and such revisions could be material. Reclassifications Certain reclassifications have been made to prior periods to conform to current period presentation. None of these reclassifications impacted previously reported stockholders' equity, cash flows, or operating income. Revenue from Contracts with Customers (Topic 606) - ASU 2014-09 In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASC 606"). ASC 606 provides a comprehensive revenue recognition standard for contracts with customers that supersedes current revenue recognition guidance including industry specific guidance and includes a five-step revenue recognition model to depict the transfer of goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. We adopted ASC 606 in the first quarter of 2018 using the modified retrospective method. The adoption of ASC 606 did not result in a cumulative effect adjustment on our opening accumulated earnings balance in our consolidated balance sheet. Results for reporting periods beginning after January 1, 2018 are presented under ASC 606, while prior period amounts are not adjusted and continue to be reported in accordance with our historical accounting under ASC 605, Revenue Recognition ("ASC 605"). Disaggregation of revenue In accordance with ASC 606, the Company disaggregates revenues from contracts with customers by product type. All of the Company's revenue is recognized at a point in time when the customer obtains control of the delivered product, which for the Company is primarily at the wellhead. The following table presents our revenues disaggregated by product type and the impact of applying ASC 606 on our current period results: Three Months Ended March 31, 2018 (in thousands) As reported (ASC 606) Historical (ASC 605) Effect of change REVENUES Oil sales $ 251,977 $ 251,977 $ — Natural gas sales 8,432 9,601 (1,169 ) NGLs sales 15,913 18,074 (2,161 ) Total revenues 276,322 279,652 (3,330 ) OPERATING EXPENSES Lease operating expenses 32,135 35,465 (3,330 ) OPERATING INCOME 130,062 130,062 — NET INCOME $ 89,573 $ 89,573 $ — Changes to revenues and lease operating expenses shown in the table above are due to the conclusion under ASC 606 that the Company meets the definition of an agent for certain of its gas processing and purchase contracts, thus the fees paid to these service providers are recorded as a deduction to revenues. In contracts where the Company meets the definition of a principal under the control model defined in ASC 606, the fees paid to these service providers are recorded as lease operating expenses. Oil, natural gas and NGLs sales We generally sell oil production at the wellhead for a contractually specified index price plus or minus a differential, less transportation costs, and recognize revenue at the net price received. Under our gas processing contracts, we deliver natural gas to a midstream processing entity at the wellhead or the inlet of the midstream processing entity’s system. For those contracts where we have concluded we are the agent and the midstream processing entity is our customer, we recognize natural gas and NGLs revenues based on the net amount of the proceeds received from the midstream processing entity. Alternatively, for those contracts where we have concluded we are the principal and the ultimate third party is our customer, we recognize revenue on a gross basis, with transportation, gathering, processing and compression fees presented as a component of lease operating expenses in our consolidated statements of operations. We record revenue in the month production is delivered to the purchaser. However, settlement statements for certain oil, natural gas and NGLs sales are typically not received for 30 to 90 days after the date production is delivered. At the end of each month, we estimate the amount of production that was delivered to the purchaser and the price that will be received. Variances between our estimates and the actual amounts received, if any, are recorded in the month payment is received. During the first quarter of 2018, revenue recognized in the reporting period related to performance obligations satisfied in prior reporting periods were not significant. Practical expedients and exemptions We do not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which the variable consideration is allocated entirely to a wholly unsatisfied performance obligation, as allowed under ASC 606. Under our sales contracts, each barrel of oil and NGLs, or Mmbtu of natural gas represents a separate performance obligation; therefore future volumes are wholly unsatisfied and disclosure of the transaction price allocated to remaining performance obligations is not required. Accounts Receivable (in thousands) As of March 31, 2018 As of December 31, 2017 Sale of oil, natural gas and NGLs $ 110,722 $ 95,942 Joint interest owners 17,141 14,880 Federal income tax receivable 335 335 Total accounts receivable $ 128,198 $ 111,157 Accounts receivable, which are primarily from the sale of oil, NGLs and natural gas, are accrued based on estimates of the volumetric sales and prices the Company believes it will receive. In addition, settled but uncollected derivative contracts, receivables related to joint interest billings and income tax receivables are included in accounts receivable. The Company routinely reviews outstanding balances, assesses the financial strength of its customers and records a reserve for amounts not expected to be fully recovered. The need for an allowance is determined based upon reviews of individual accounts, historical losses, existing economic conditions and other pertinent factors. Bad debt expense was zero for the three months ended March 31, 2018 and 2017 , respectively. Oil and Natural Gas Properties The Company uses the successful efforts method of accounting for its oil and natural gas exploration and production activities. Costs incurred by the Company related to the acquisition of oil and natural gas properties and the cost of drilling development wells and successful exploratory wells are capitalized, while the costs of unsuccessful exploratory wells are expensed when determined to be unsuccessful. The Company may capitalize interest on expenditures for significant exploration and development projects that last more than six months , while activities are in progress to bring the assets to their intended use. The Company has not capitalized any interest as projects generally lasted less than six months . Costs incurred to maintain wells and related equipment, lease and well operating costs and other exploration costs are expensed as incurred. Capitalized acquisition costs attributable to proved oil and natural gas properties and leasehold costs are depleted using the unit-of-production method based on proved reserves. Capitalized exploration well costs and development costs, including AROs, are depleted using the unit-of-production method based on proved developed reserves. For the three months ended March 31, 2018 and 2017 , depletion expense for oil and natural gas producing property was $75.4 million and $60.4 million , respectively. Depletion expense is included in depreciation, depletion and amortization in the accompanying consolidated statements of operations. The Company’s oil and natural gas properties as of March 31, 2018 and December 31, 2017 consisted of the following: (in thousands) March 31, 2018 December 31, 2017 Proved oil and natural gas properties $ 4,189,377 $ 3,936,565 Unproved oil and natural gas properties 2,859,631 2,865,952 Total oil and natural gas properties 7,049,008 6,802,517 Less: Accumulated depletion (853,720 ) (778,596 ) Total oil and natural gas properties, net $ 6,195,288 $ 6,023,921 In some circumstances, it may be uncertain whether proved commercial reserves have been found when drilling has been completed. Such exploratory well drilling costs may continue to be capitalized if the anticipated reserve quantity is sufficient to justify its completion as a producing well and sufficient progress in assessing the reserves and the economic and operating viability of the project is being made. As of March 31, 2018 and December 31, 2017 , there were no costs capitalized in connection with exploratory wells in progress. Proved oil and natural gas properties are evaluated for impairment annually or whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable. These assets are reviewed for potential impairment at the lowest level for which there are identifiable cash flows available which is the level at which depletion is calculated. To determine if an asset is impaired, the Company compares the carrying value of the asset to the undiscounted future net cash flows by applying estimates of future oil, NGLs and natural gas prices to the estimated future production of oil, NGLs and natural gas reserves over the economic life of the asset and deducting future costs. Future net cash flows are based upon our reservoir engineers’ estimates of proved reserves and risk-adjusted probable reserves. For a property determined to be impaired, an impairment loss equal to the difference between the asset’s carrying value and its estimated fair value is recognized. Fair value is estimated to be the present value of the aforementioned expected future net cash flows. Each part of this calculation is subject to a large degree of judgment, including the determination of the depletable units’ estimated reserves, future net cash flows and fair value. No impairment of proved property was recorded for the three months ended March 31, 2018 or 2017 . The calculation of expected future net cash flows in impairment evaluations are primarily based on estimates of future oil and natural gas prices, proved reserves and risk-adjusted probable reserve quantities, and estimates of future production and capital costs associated with our proved and risk-adjusted probable reserves. The Company’s estimates for future oil and natural gas prices used in the impairment evaluations are based on observable prices for the next three years, and then held constant for the remaining lives of the properties. Unproved property costs and related leasehold expirations are assessed quarterly for potential impairment and when industry conditions dictate an impairment may be possible. For the three months ended March 31, 2018 and 2017 , we impaired approximately $4.2 million and $0.1 million , respectively, of unproved oil and natural gas properties, which primarily related to management’s expectation that certain leasehold interests would expire and not be renewed. Proceeds from the sales of individual oil and natural gas properties that are part of a depletion base are credited to accumulated depletion with no immediate impact on income until the entire depletion base is sold. However, gain or loss is recognized if the disposition is significant enough to materially impact the depletion rate of the remaining properties in the depletion base. Gains and losses arising from the sale of properties are generally included in operating income. Accrued Expenses Accrued expenses consist of the following: (in thousands) March 31, 2018 December 31, 2017 Accrued capital expenditures $ 91,372 $ 82,748 Other accrued expenses 25,000 36,691 Accrued expenses $ 116,372 $ 119,439 Asset Retirement Obligation The Company records AROs related to the retirement of long-lived assets at the time a legal obligation is incurred and the liability can be reasonably estimated. AROs are recorded as long-term liabilities with a corresponding increase in the carrying amount of the related long-lived asset. Subsequently, the asset retirement cost included in the carrying amount of the related asset is allocated to expense through depletion of the asset. Changes in the liability due to passage of time are generally recognized as an increase in the carrying amount of the liability and as corresponding accretion expense. The Company estimates a fair value of the obligation on each well in which it owns an interest by identifying costs associated with the future down-hole plugging, dismantlement and removal of production equipment and facilities, and the restoration and reclamation of the surface acreage to a condition similar to that existing before oil and natural gas extraction began. In general, the amount of ARO and the costs capitalized will be equal to the estimated future cost to satisfy the abandonment obligation using current prices that are escalated by an assumed inflation factor up to the estimated settlement date which is then discounted back to the date that the abandonment obligation was incurred using an estimated credit adjusted rate. If the estimated ARO changes, an adjustment is recorded to both the ARO liability and the long-lived asset. Revisions to estimated AROs can result from changes in retirement cost estimates, revisions to estimated inflation rates and changes in the estimated timing of abandonment. After recording these amounts, the ARO liability is accreted to its future estimated value using the same assumed credit adjusted rate and the associated capitalized costs are depreciated on a unit-of-production basis. The following is a reconciliation of our ARO liability for the three months ended March 31, 2018: (in thousands) Asset retirement obligation at beginning of period $ 15,849 Liabilities incurred 789 Liabilities settled (278 ) Accretion expense 205 Asset retirement obligation at end of period $ 16,565 Income Taxes The following is an analysis of the Company’s consolidated income tax expense for the periods indicated: Three Months Ended March 31, (in thousands) 2018 2017 Current $ — $ 1,498 Deferred 21,932 13,574 Income Tax Expense $ 21,932 $ 15,072 Deferred taxes are determined based on the estimated future tax effects of differences between the financial statement carrying amounts and tax basis of assets and liabilities, given the provisions of enacted tax laws. Tax positions are evaluated for recognition using a more-likely-than-not threshold, and those tax positions requiring recognition are measured as the largest amount of tax benefit that is greater than fifty percent likely of being realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. The Company’s policy is to record interest and penalties relating to uncertain tax positions in income tax expense. We have not recognized any interest and penalties relating to unrecognized tax benefits in our consolidated financial statements. New Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”). ASU 2016-02 generally requires all lease transactions (with expected lease terms in excess of 12 months) to be recognized on the balance sheet as lease assets and lease liabilities. Public entities are required to apply ASU 2016-02 for annual and interim reporting periods beginning after December 15, 2018 with early adoption permitted. We do not plan to early adopt the standard. We are currently evaluating the impact of ASU 2016-02 on our consolidated financial statements.

Acquisitions of Oil and Natural

Acquisitions of Oil and Natural Gas Property Interests	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
Acquisitions of Oil and Natural Gas Property Interests	ACQUISITIONS OF OIL AND NATURAL GAS PROPERTY INTERESTS During the first quarter of 2018, we closed on bolt-on acquisitions of undeveloped acreage in the Delaware Basin for an aggregate total purchase price of $8.7 million .

Derivative Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	DERIVATIVE INSTRUMENTS Commodity Derivative Instruments The Company uses derivative instruments to manage its exposure to cash-flow variability from commodity-price risk inherent in its crude oil and natural gas production. The derivative instruments are recorded at fair value on the consolidated balance sheets and any gains and losses are recognized in current period earnings. Our commodity derivatives are comprised of the following instruments: Collars : Each collar transaction has an established price floor and ceiling, and certain collar transactions also include a short put. When the settlement price is below the price floor established by these collars, the Company receives an amount from its counterparty equal to the difference between the settlement price and the price floor multiplied by the hedged contract volume. When the settlement price is above the price ceiling established by these collars, the Company pays its counterparty an amount equal to the difference between the settlement price and the price ceiling multiplied by the hedged contract volume. When the settlement price is below the short put price, the Company receives from its counterparty an amount equal to the difference of the price floor and the short put price multiplied by the hedged contract volume. Swaps : Each swap transaction has an established fixed price. When the settlement price is above the fixed price, the Company pays its counterparty an amount equal to the difference between the settlement price and the fixed price multiplied by the hedged contract volume. When the settlement price is below the fixed price, the counterparty pays the Company an amount equal to the difference between the settlement price and the fixed price multiplied by the hedged contract volume. The following table summarizes all commodity derivative positions as of March 31, 2018 : Contracts expiring in the period ending: June 30, 2018 September 30, 2018 December 31, 2018 2019 Oil Three-Way Collars: Notional volume (Bbl) 1,941,000 1,319,000 1,227,000 — Weighted average ceiling price ($/Bbl)(1) $ 59.07 $ 60.56 $ 60.96 $ — Weighted average floor price ($/Bbl)(1) $ 47.11 $ 47.79 $ 48.00 $ — Weighted average short put price ($/Bbl)(1) $ 37.11 $ 37.79 $ 38.00 $ — Oil Costless Collars: Notional volume (Bbl) 516,000 1,212,000 1,058,000 2,555,000 Weighted average ceiling price ($/Bbl)(1) $ 60.20 $ 60.10 $ 60.11 $ 58.04 Weighted average floor price ($/Bbl)(1) $ 45.00 $ 46.33 $ 46.52 $ 52.50 Oil Swaps: Notional volume (Bbl) 698,000 322,000 322,000 2,555,000 Weighted average swap price ($/Bbl)(1) $ 62.97 $ 55.77 $ 55.77 $ 55.74 Mid-Cush Differential (Basis) Swaps: Notional volume (Bbl) 2,730,000 2,760,000 2,760,000 2,555,000 Weighted average swap price ($/Bbl)(2) $ (0.42 ) $ (0.42 ) $ (0.42 ) $ (0.29 ) (1) The oil derivative contracts are settled based on the arithmetic average of the closing settlement price for the front month contract NYMEX price of West Texas Intermediate Light Sweet Crude. (2) The Mid-Cush swap contracts are settled based on the difference in the arithmetic average during the calculation period of WTI MIDLAND ARGUS and WTI ARGUS prices in the Argus Americas Crude publication for the relevant period. Derivative Fair Values and Gains The following table presents the fair value of our derivative instruments. Our derivatives are presented as separate line items in our consolidated balance sheets as current and noncurrent derivative instrument assets and liabilities based on the expected settlement dates of the instruments. The Company has agreements in place with all of its counterparties that allow for the financial right of offset for derivative assets and derivative liabilities at settlement or in the event of a default under the agreements. However, the fair value amounts are presented on a gross basis in our consolidated balance sheets and do not reflect the netting of asset and liability positions permitted under the terms of the Company’s master netting arrangements. See Note 5 for further discussion related to the fair value of the Company’s derivatives. Assets Liabilities (in thousands) March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 Derivative Instruments: Current amounts $ 30,186 $ 64 $ 51,001 $ 36,566 Noncurrent amounts 4,574 37 9,321 5,722 Total derivative instruments $ 34,760 $ 101 $ 60,322 $ 42,288 Gains and losses on derivatives are reported in the consolidated statements of operations. The following represents the Company’s reported gains on derivative instruments for the periods presented: Three Months Ended March 31, (in thousands) 2018 2017 Net gain on derivative instruments $ 2,907 $ 17,121 Credit-Risk Related Contingent Features in Derivatives None of the Company’s derivative instruments contain credit-risk related contingent features. No amounts of collateral were posted by the Company related to net positions as of March 31, 2018 and December 31, 2017 .

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS We value our derivatives and other financial instruments according to FASB ASC 820, Fair Value Measurements and Disclosures , which defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (“exit price”) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The Company has categorized its assets and liabilities measured at fair value, based on the priority of inputs to the valuation technique, into a three-level fair value hierarchy. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). Assets and liabilities recorded at fair value on the consolidated balance sheets are categorized based on the inputs to the valuation techniques as follows: • Level 1—Assets and liabilities recorded at fair value for which values are based on unadjusted quoted prices for identical assets or liabilities in an active market that management has the ability to access. Active markets are considered to be those in which transactions for the assets or liabilities occur in sufficient frequency and volume to provide pricing information on an ongoing basis. • Level 2—Assets and liabilities recorded at fair value for which values are based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly for substantially the full term of the asset or liability. Substantially all of these inputs are observable in the marketplace throughout the full term of the price risk management instrument and can be derived from observable data or supported by observable levels at which transactions are executed in the marketplace. • Level 3—Assets and liabilities recorded at fair value for which values are based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. Unobservable inputs that are not corroborated by market data and may reflect management's own assumptions about the assumptions a market participant would use in pricing the asset or liability. Valuation techniques that maximize the use of observable inputs are favored. Assets and liabilities are classified in their entirety based on the lowest priority level of input that is significant to the fair value measurement. The assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the placement of assets and liabilities within the levels of the fair value hierarchy. Reclassifications of fair value among Level 1, Level 2 and Level 3 of the fair value hierarchy, if applicable, are made at the end of each quarter. There were no transfers among Level 1, Level 2 or Level 3 during the three months ended March 31, 2018 . Fair Value Measurement on a Recurring Basis Fair value of commodity derivative instruments The fair value of derivative financial instruments is determined utilizing industry standard models incorporating assumptions and inputs, most of which are substantially observable in active markets throughout the full term of the instruments. These include market price curves, contract terms and prices, credit risk adjustments, implied market volatility and discount factors. The following table presents a summary of the estimated net fair value of our commodity derivative instruments as of March 31, 2018 and December 31, 2017 . (in thousands) Level 1 Level 2 Level 3 Total fair value As of March 31, 2018: Commodity derivative instruments $ — $ (25,562 ) $ — $ (25,562 ) (in thousands) Level 1 Level 2 Level 3 Total fair value As of December 31, 2017: Commodity derivative instruments $ — $ (42,187 ) $ — $ (42,187 ) Fair value of other financial instruments Our financial instruments include cash and cash equivalents, accounts receivable and payable and accrued expenses. The carrying amount of these instruments approximates fair value because of their short-term nature. The carrying value of our borrowings under our revolving credit facility ("Revolving Credit Facility") approximate fair value as these are subject to short-term floating interest rates that approximate the rates available to us for those periods. The estimated fair values of our senior notes are presented below. The estimated fair value of our 5.25% senior unsecured notes due January 15, 2025 (“2025 Senior Notes”) and 6.625% senior unsecured notes due October 1, 2022 (“2022 Senior Notes”) have been calculated based on quoted prices in active markets and are classified as Level 1. The following table presents a summary of the estimated fair value of our senior notes as of March 31, 2018 and December 31, 2017. March 31, 2018 (in thousands) Level 1 Level 2 Level 3 Total fair value 2025 Senior Notes $ 466,340 $ — $ — $ 466,340 2022 Senior Notes 732,963 — — 732,963 December 31, 2017 (in thousands) Level 1 Level 2 Level 3 Total fair value 2025 Senior Notes $ 464,022 $ — $ — $ 464,022 2022 Senior Notes 734,706 — — 734,706 Nonfinancial Assets and Liabilities Assets and liabilities acquired in business combinations are recorded at their fair value on the date of acquisition. Significant Level 3 assumptions associated with the calculation of future cash flows used in the analysis of fair value of the oil and natural gas property acquired include the Company’s estimate of future commodity prices, production costs, development expenditures, production, risk-adjusted discount rates and other relevant data. Additionally, fair value is used to determine the inception value of the Company’s AROs. The inputs used to determine such fair value are primarily based upon assumptions of the estimated current abandonment costs, discount rate, inflation rate and timing associated with the incurrence of these costs. Our estimated abandonment costs are obtained primarily from independent third parties for costs that would be incurred to restore leased property to the contractually stipulated condition or costs incurred historically for similar work. Additions to the Company’s AROs represent a nonrecurring Level 3 measurement. The Company reviews its proved oil and natural gas properties for impairment purposes by comparing the expected undiscounted future cash flows at a producing field level to the unamortized capitalized cost of the asset. Significant assumptions associated with the calculation of future cash flows used in the impairment analysis include the estimate of future commodity prices, production costs, development expenditures, production, risk-adjusted discount rates and other relevant data. As such, the fair value of oil and natural gas properties used in estimating impairment represents a nonrecurring Level 3 measurement.

Long-Term Debt

Long-Term Debt	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Long-Term Debt	LONG-TERM DEBT Long-term debt consists of the following: (in thousands) March 31, 2018 December 31, 2017 Revolving Credit Facility $ 445,000 $ 375,000 5.25% Senior Notes due 2025 450,000 450,000 6.625% Senior Notes due 2022 700,000 700,000 Less: Discount (900 ) (950 ) Less: Debt issuance costs (14,349 ) (14,922 ) Total long-term debt $ 1,579,751 $ 1,509,128 Revolving Credit Facility As of March 31, 2018 , the borrowing base under our amended and restated credit agreement was $1.5 billion , with a Company-elected commitment of $900.0 million , and lender commitments of $2.5 billion . The maturity date of the Revolving Credit Facility is December 19, 2021. The borrowing base under the Revolving Credit Facility remains subject to semi-annual review and redetermination by the lenders pursuant to the term of the credit agreement. The redetermination of the borrowing base occurs in May and November of each year and, among other things, depends on the volumes of proved oil, NGLs and natural gas reserves and an estimate of associated cash flows, and commodity hedge positions. As of March 31, 2018 , we had $445.0 million in borrowings, $1.9 million of letters of credit outstanding and $453.1 million of borrowing capacity under our Revolving Credit Facility. The Company's credit agreement requires that we maintain the following two financial ratios: • a working capital ratio, which is the ratio of consolidated current assets (includes unused commitments under its Revolving Credit Facility and excludes restricted cash and derivative assets) to consolidated current liabilities (excluding the current portion of long-term debt under the Revolving Credit Facility and derivative liabilities), of not less than 1.0 to 1.0; • a leverage ratio, which is the ratio of the sum of all of the Company’s debt to the consolidated EBITDAX (as defined in the credit agreement) for the four fiscal quarters then ended, of not greater than 4.25 to 1.0. Our credit agreement also contains restrictive covenants that may limit our ability to, among other things, incur additional indebtedness, make loans to others, make investments, enter into mergers, make or declare dividends, enter into commodity hedges exceeding a specified percentage or our expected production, enter into interest rate hedges exceeding a specified percentage of our outstanding indebtedness, incur liens, sell assets, enter into transactions with affiliates or engage in certain other transactions without the prior consent of the lenders. The Company was in compliance with such covenants and ratios as of March 31, 2018 . Principal amounts borrowed under our Revolving Credit Facility are payable on the maturity date, and interest is payable quarterly for base rate loans and at the end of the applicable interest period for Eurodollar loans. We have a choice of borrowing at a Eurodollar rate or at the adjusted base rate. Eurodollar loans bear interest at a rate per annum equal to an adjusted London Interbank Offered Rate (“LIBOR”) (equal to the quotient of: (i) the LIBOR rate; divided by (ii) a percentage equal to 100% minus the maximum rate on such date at which the administrative agent is required to maintain reserves on “Eurocurrency Liabilities,” as defined in and pursuant to Regulation D of the Board of Governors of the Federal Reserve System) plus an applicable margin ranging from 150 basis points to 250 basis points , depending on the percentage of our borrowing base utilized. Alternate base rate loans bear interest at a rate per annum equal to the greatest of: (i) the agent bank’s referenced rate; (ii) the federal funds effective rate plus 50 basis points ; and (iii) the adjusted LIBOR rate plus 100 basis points , plus an applicable margin ranging from 50 basis points to 150 basis points , depending on the percentage of our borrowing base utilized, plus a commitment fee ranging from 37.5 basis points to 50 basis points charged on the undrawn commitment amount. On March 31, 2018 , our weighted average interest rate was approximately 3.9% . 2025 Senior Notes On December 27, 2016, the Company issued $450.0 million of 5.25% senior unsecured notes at par through a private placement. In November 2017, the Company exchanged these notes for registered notes with the same terms. The 2025 Senior Notes will mature on January 15, 2025. The notes are senior unsecured obligations that rank equally with all of our future senior indebtedness, are effectively subordinated in rights to our assets constituting collateral held by all our existing and future secured indebtedness to the extent of the value of the collateral securing such indebtedness, including indebtedness under our Revolving Credit Facility, and will rank senior to any future subordinated indebtedness of the Company. Interest on the 2025 Senior Notes is payable semi-annually on January 15 and July 15. On or after January 15, 2020, the Company may redeem some or all of the 2025 Senior Notes, with certain restrictions, at a redemption price, plus accrued and unpaid interest, of 103.938% of principal, declining in twelve-month intervals to 100% in 2023 and thereafter. In addition, prior to January 15, 2020, on any one or more occasions, the Company may redeem all or part of the 2025 Senior Notes at a redemption price of 100% of the principal amount of the notes redeemed, plus an applicable make-whole premium along with accrued and unpaid interest. In the event of certain changes in control of the Company, each holder of the 2025 Senior Notes will have the right to require us to repurchase all or any part of the notes at a purchase price in cash equal to 101% of the principal amount, plus accrued and unpaid interest to the date of purchase. The 2025 Senior Notes are guaranteed on a senior unsecured basis by each of our consolidated subsidiaries. The subsidiary guarantees are full and unconditional and joint and several, and any of our subsidiaries other than the subsidiary guarantors are minor. RSP Inc. does not have independent assets or operations. The terms of the notes include, among other restrictions, limitations on our ability to repurchase shares, incur debt, create liens, make investments, transfer or sell assets, enter into transactions with affiliates and consolidate, merge or transfer all or substantially all of our assets. The Company was in compliance with the provisions of the indenture governing the 2025 Senior Notes as of March 31, 2018 . 2022 Senior Notes On September 26, 2014, the Company issued $500.0 million of 6.625% senior unsecured notes at par through a private placement. In June 2015, the Company exchanged these notes for registered notes with the same terms. On August 10, 2015, the Company issued an additional $200.0 million of the 6.625% senior unsecured notes at 99.25% of the principal amount through a private placement. In March 2016, the Company exchanged these additional notes for registered notes with the same terms. The 2022 Senior Notes will mature on October 1, 2022. The notes are senior unsecured obligations that rank equally with all of our future senior indebtedness, are effectively subordinated to all our existing and future secured indebtedness to the extent of the value of the collateral securing such indebtedness, including borrowings under our Revolving Credit Facility, and will rank senior to any future subordinated indebtedness of the Company. Interest on the 2022 Senior Notes is payable semi-annually on April 1 and October 1. The Company may redeem some or all of the notes, with certain restrictions, at a redemption price, plus accrued and unpaid interest, of 104.969% of principal, declining in twelve-month intervals to 100% in 2020 and thereafter. In the event of certain changes in control of the Company, each holder of the 2022 Senior Notes will have the right to require us to repurchase all or any part of the notes at a purchase price in cash equal to 101% of the principal amount, plus accrued and unpaid interest to the date of purchase. The 2022 Senior Notes are guaranteed on a senior unsecured basis by each of our consolidated subsidiaries. The subsidiary guarantees are full and unconditional and joint and several, and any subsidiaries of the Company other than the subsidiary guarantors are minor. The terms of the notes include, among other restrictions, limitations on our ability to repurchase shares, incur debt, create liens, make investments, transfer or sell assets, enter into transactions with affiliates and consolidate, merge or transfer all or substantially all of our assets. The Company was in compliance with the provisions of the indenture governing the 2022 Senior Notes as of March 31, 2018 .

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Legal and Environmental Matters The Company is party to proceedings and claims incidental to its business. While many of these matters involve inherent uncertainty, the Company believes that the amount of the liability, if any, ultimately incurred with respect to any such proceedings or claims will not have a material adverse effect, individually or in the aggregate, on the Company's consolidated financial position as a whole or on its liquidity, capital resources or future results of operations. The Company will continue to evaluate proceedings and claims involving the Company on a regular basis and will establish and adjust any reserves as appropriate to reflect its assessment of the then-current status of the matters. The Company is subject to various federal, state and local laws and regulations relating to the protection of the environment. These laws, which are often changing, regulate the discharge of materials into the environment and may require the Company to remove or mitigate the environmental effects of the disposal or release of petroleum or chemical substances at various sites. Environmental expenditures are expensed as incurred. We have established procedures for the ongoing evaluation of our operations to identify potential environmental exposures and to comply with regulatory policies and procedures. Environmental expenditures that relate to current operations are expensed or capitalized as appropriate. Expenditures that relate to an existing condition caused by past operations, which do not contribute to current or future revenue generation, are expensed. Liabilities are recorded when we determine the potential exposure related to, but not limited to, legal matters, environmental assessments and/or clean-ups, is probable and estimable. Such liabilities are generally undiscounted unless the timing of cash payments is fixed and readily determinable. At both March 31, 2018 and December 31, 2017 , the Company had no environmental matters requiring specific disclosure or requiring the recognition of a liability. Contractual Obligations For the three months ended March 31, 2018 , the Company had no material changes in its contractual commitments and obligations from amounts listed in Note 7 in the notes to our consolidated financial statements in our Annual Report on Form 10-K for the year ended December 31, 2017 .

Equity-Based Compensation

Equity-Based Compensation	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity-Based Compensation	EQUITY-BASED COMPENSATION The Company's 2014 Long Term Incentive Plan ("LTIP") provides for granting restricted stock awards and performance-based restricted stock awards to employees, consultants and directors of the Company and its affiliates who perform services for the Company. Equity-based compensation expense, which was recorded in general and administrative expenses, was $5.3 million and $3.9 million for the three months ended March 31, 2018 and 2017 , respectively. Restricted Stock Awards The following table represents restricted stock award activity for the three months ended March 31, 2018: Shares Weighted Average Fair Value Restricted shares outstanding, beginning of period 687,277 $ 32.04 Restricted shares granted 437,608 35.96 Restricted shares canceled (770 ) 30.66 Restricted shares vested (320,001 ) 30.04 Restricted shares outstanding, end of period 804,114 $ 34.97 As of March 31, 2018 , the Company had unrecognized compensation expense of $26.3 million related to restricted stock awards which is expected to be recognized over a weighted average period of 2.2 years. Performance-Based Restricted Stock Awards We granted performance-based restricted stock awards to certain officers of the Company. The payout of these awards varies depending on the Company’s total shareholder return in comparison to an identified peer group. We granted 496,537 performance-based restricted stock awards in February 2018 that allow for a payout between 0% and 100% , with a cliff vesting period of three years. The following table represents performance-based restricted stock award activity for the three months ended March 31, 2018: Shares Weighted Average Fair Value Restricted shares outstanding, beginning of period 1,001,079 $ 21.14 Restricted shares granted (1) 496,537 23.96 Restricted shares vested (1) (143,824 ) 31.74 Restricted shares outstanding, end of period 1,353,792 $ 21.05 (1) Performance-based restricted shares granted or vested reflect the number of shares granted or vested at a 100% of the target payout. The actual payout of the shares granted may be between 0% and 200% depending on the date of the grant and Company’s total shareholder return in comparison to an identified peer group. As of March 31, 2018 , the Company had unrecognized compensation expense of $19.4 million related to performance-based restricted stock awards which is expected to be recognized over a weighted average period of 1.8 years.

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE The Company’s basic earnings per share amounts have been computed using the two-class method based on the weighted-average number of shares of common stock outstanding for the period. A reconciliation of the components of basic and diluted earnings per common share is presented in the table below: Three Months Ended March 31, (in thousands, except per share data) 2018 2017 Numerator: Net income available to stockholders $ 89,573 $ 38,934 Basic net income allocable to participating securities (1) 448 195 Income available to stockholders $ 89,125 $ 38,739 Denominator: Weighted average number of common shares outstanding - basic 157,119 146,054 Effect of dilutive securities: Restricted stock 1,190 951 Weighted average number of common shares outstanding - diluted 158,309 147,005 Net earnings per share: Basic $ 0.57 $ 0.27 Diluted $ 0.57 $ 0.26 (1) Restricted share awards that contain non-forfeitable rights to dividends are participating securities and, therefore, are included in computing earnings using the two-class method. Participating securities, however, do not participate in undistributed net losses.

Summary of Significant Accoun16

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the SEC and are presented in accordance with generally accepted accounting principles in the United States (“GAAP”). They reflect all adjustments that are, in the opinion of management, necessary for a fair presentation. The consolidated financial statements of the Company include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Certain information, accounting policies, and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States have been omitted pursuant to such rules and regulations, although the Company believes the disclosures are adequate to make the information presented not misleading. The financial statements in this Quarterly Report on Form 10–Q should be read together with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 , which contains a complete summary of the Company’s significant accounting policies and disclosures.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the financial statements and accompanying notes. The more significant estimates pertain to proved oil, natural gas liquids ("NGLs") and natural gas reserves, asset retirement obligations (“AROs”), equity-based compensation, estimates relating to oil, NGLs and natural gas revenues and expenses, accrued liabilities, the fair market value of assets and liabilities acquired in business combinations, derivatives and income taxes. Although management believes these estimates are reasonable, actual results could differ from these estimates. Changes in estimates are recorded prospectively. Significant assumptions are required in the valuation of proved oil, NGLs and natural gas reserves that may affect the amount at which oil and natural gas properties are recorded. Depletion of oil and natural gas properties are determined using estimates of proved oil, NGLs and natural gas reserves. There are numerous uncertainties inherent in the estimation of quantities of proved reserves and in the projection of future rates of production and the timing of development expenditures. Similarly, evaluations for impairment of proved and unproved oil and natural gas properties are subject to numerous uncertainties including, among others, estimates of future recoverable reserves and commodity price estimates. It is possible that these estimates could be revised at future dates and such revisions could be material.
Reclassifications	Reclassifications Certain reclassifications have been made to prior periods to conform to current period presentation. None of these reclassifications impacted previously reported stockholders' equity, cash flows, or operating income.
Revenue from Contracts with Customers (Topic 606) - ASU 2014-09	Revenue from Contracts with Customers (Topic 606) - ASU 2014-09 In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASC 606"). ASC 606 provides a comprehensive revenue recognition standard for contracts with customers that supersedes current revenue recognition guidance including industry specific guidance and includes a five-step revenue recognition model to depict the transfer of goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. We adopted ASC 606 in the first quarter of 2018 using the modified retrospective method. The adoption of ASC 606 did not result in a cumulative effect adjustment on our opening accumulated earnings balance in our consolidated balance sheet. Results for reporting periods beginning after January 1, 2018 are presented under ASC 606, while prior period amounts are not adjusted and continue to be reported in accordance with our historical accounting under ASC 605, Revenue Recognition ("ASC 605"). Disaggregation of revenue In accordance with ASC 606, the Company disaggregates revenues from contracts with customers by product type. All of the Company's revenue is recognized at a point in time when the customer obtains control of the delivered product, which for the Company is primarily at the wellhead. The following table presents our revenues disaggregated by product type and the impact of applying ASC 606 on our current period results: Three Months Ended March 31, 2018 (in thousands) As reported (ASC 606) Historical (ASC 605) Effect of change REVENUES Oil sales $ 251,977 $ 251,977 $ — Natural gas sales 8,432 9,601 (1,169 ) NGLs sales 15,913 18,074 (2,161 ) Total revenues 276,322 279,652 (3,330 ) OPERATING EXPENSES Lease operating expenses 32,135 35,465 (3,330 ) OPERATING INCOME 130,062 130,062 — NET INCOME $ 89,573 $ 89,573 $ — Changes to revenues and lease operating expenses shown in the table above are due to the conclusion under ASC 606 that the Company meets the definition of an agent for certain of its gas processing and purchase contracts, thus the fees paid to these service providers are recorded as a deduction to revenues. In contracts where the Company meets the definition of a principal under the control model defined in ASC 606, the fees paid to these service providers are recorded as lease operating expenses. Oil, natural gas and NGLs sales We generally sell oil production at the wellhead for a contractually specified index price plus or minus a differential, less transportation costs, and recognize revenue at the net price received. Under our gas processing contracts, we deliver natural gas to a midstream processing entity at the wellhead or the inlet of the midstream processing entity’s system. For those contracts where we have concluded we are the agent and the midstream processing entity is our customer, we recognize natural gas and NGLs revenues based on the net amount of the proceeds received from the midstream processing entity. Alternatively, for those contracts where we have concluded we are the principal and the ultimate third party is our customer, we recognize revenue on a gross basis, with transportation, gathering, processing and compression fees presented as a component of lease operating expenses in our consolidated statements of operations. We record revenue in the month production is delivered to the purchaser. However, settlement statements for certain oil, natural gas and NGLs sales are typically not received for 30 to 90 days after the date production is delivered. At the end of each month, we estimate the amount of production that was delivered to the purchaser and the price that will be received. Variances between our estimates and the actual amounts received, if any, are recorded in the month payment is received. During the first quarter of 2018, revenue recognized in the reporting period related to performance obligations satisfied in prior reporting periods were not significant. Practical expedients and exemptions We do not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which the variable consideration is allocated entirely to a wholly unsatisfied performance obligation, as allowed under ASC 606. Under our sales contracts, each barrel of oil and NGLs, or Mmbtu of natural gas represents a separate performance obligation; therefore future volumes are wholly unsatisfied and disclosure of the transaction price allocated to remaining performance obligations is not required.
Accounts Receivable	Accounts receivable, which are primarily from the sale of oil, NGLs and natural gas, are accrued based on estimates of the volumetric sales and prices the Company believes it will receive. In addition, settled but uncollected derivative contracts, receivables related to joint interest billings and income tax receivables are included in accounts receivable. The Company routinely reviews outstanding balances, assesses the financial strength of its customers and records a reserve for amounts not expected to be fully recovered. The need for an allowance is determined based upon reviews of individual accounts, historical losses, existing economic conditions and other pertinent factors.
Oil and Natural Gas Properties	In some circumstances, it may be uncertain whether proved commercial reserves have been found when drilling has been completed. Such exploratory well drilling costs may continue to be capitalized if the anticipated reserve quantity is sufficient to justify its completion as a producing well and sufficient progress in assessing the reserves and the economic and operating viability of the project is being made. As of March 31, 2018 and December 31, 2017 , there were no costs capitalized in connection with exploratory wells in progress. Proved oil and natural gas properties are evaluated for impairment annually or whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable. These assets are reviewed for potential impairment at the lowest level for which there are identifiable cash flows available which is the level at which depletion is calculated. To determine if an asset is impaired, the Company compares the carrying value of the asset to the undiscounted future net cash flows by applying estimates of future oil, NGLs and natural gas prices to the estimated future production of oil, NGLs and natural gas reserves over the economic life of the asset and deducting future costs. Future net cash flows are based upon our reservoir engineers’ estimates of proved reserves and risk-adjusted probable reserves. For a property determined to be impaired, an impairment loss equal to the difference between the asset’s carrying value and its estimated fair value is recognized. Fair value is estimated to be the present value of the aforementioned expected future net cash flows. Each part of this calculation is subject to a large degree of judgment, including the determination of the depletable units’ estimated reserves, future net cash flows and fair value. No impairment of proved property was recorded for the three months ended March 31, 2018 or 2017 . The calculation of expected future net cash flows in impairment evaluations are primarily based on estimates of future oil and natural gas prices, proved reserves and risk-adjusted probable reserve quantities, and estimates of future production and capital costs associated with our proved and risk-adjusted probable reserves. The Company’s estimates for future oil and natural gas prices used in the impairment evaluations are based on observable prices for the next three years, and then held constant for the remaining lives of the properties. Unproved property costs and related leasehold expirations are assessed quarterly for potential impairment and when industry conditions dictate an impairment may be possible. For the three months ended March 31, 2018 and 2017 , we impaired approximately $4.2 million and $0.1 million , respectively, of unproved oil and natural gas properties, which primarily related to management’s expectation that certain leasehold interests would expire and not be renewed. Proceeds from the sales of individual oil and natural gas properties that are part of a depletion base are credited to accumulated depletion with no immediate impact on income until the entire depletion base is sold. However, gain or loss is recognized if the disposition is significant enough to materially impact the depletion rate of the remaining properties in the depletion base. Gains and losses arising from the sale of properties are generally included in operating income. Oil and Natural Gas Properties The Company uses the successful efforts method of accounting for its oil and natural gas exploration and production activities. Costs incurred by the Company related to the acquisition of oil and natural gas properties and the cost of drilling development wells and successful exploratory wells are capitalized, while the costs of unsuccessful exploratory wells are expensed when determined to be unsuccessful. The Company may capitalize interest on expenditures for significant exploration and development projects that last more than six months , while activities are in progress to bring the assets to their intended use. The Company has not capitalized any interest as projects generally lasted less than six months . Costs incurred to maintain wells and related equipment, lease and well operating costs and other exploration costs are expensed as incurred. Capitalized acquisition costs attributable to proved oil and natural gas properties and leasehold costs are depleted using the unit-of-production method based on proved reserves. Capitalized exploration well costs and development costs, including AROs, are depleted using the unit-of-production method based on proved developed reserves. For the three months ended March 31, 2018 and 2017 , depletion expense for oil and natural gas producing property was $75.4 million and $60.4 million , respectively. Depletion expense is included in depreciation, depletion and amortization in the accompanying consolidated statements of operations.
Asset Retirement Obligation	Asset Retirement Obligation The Company records AROs related to the retirement of long-lived assets at the time a legal obligation is incurred and the liability can be reasonably estimated. AROs are recorded as long-term liabilities with a corresponding increase in the carrying amount of the related long-lived asset. Subsequently, the asset retirement cost included in the carrying amount of the related asset is allocated to expense through depletion of the asset. Changes in the liability due to passage of time are generally recognized as an increase in the carrying amount of the liability and as corresponding accretion expense. The Company estimates a fair value of the obligation on each well in which it owns an interest by identifying costs associated with the future down-hole plugging, dismantlement and removal of production equipment and facilities, and the restoration and reclamation of the surface acreage to a condition similar to that existing before oil and natural gas extraction began. In general, the amount of ARO and the costs capitalized will be equal to the estimated future cost to satisfy the abandonment obligation using current prices that are escalated by an assumed inflation factor up to the estimated settlement date which is then discounted back to the date that the abandonment obligation was incurred using an estimated credit adjusted rate. If the estimated ARO changes, an adjustment is recorded to both the ARO liability and the long-lived asset. Revisions to estimated AROs can result from changes in retirement cost estimates, revisions to estimated inflation rates and changes in the estimated timing of abandonment. After recording these amounts, the ARO liability is accreted to its future estimated value using the same assumed credit adjusted rate and the associated capitalized costs are depreciated on a unit-of-production basis. Fair value of other financial instruments Our financial instruments include cash and cash equivalents, accounts receivable and payable and accrued expenses. The carrying amount of these instruments approximates fair value because of their short-term nature. The carrying value of our borrowings under our revolving credit facility ("Revolving Credit Facility") approximate fair value as these are subject to short-term floating interest rates that approximate the rates available to us for those periods. The estimated fair values of our senior notes are presented below. The estimated fair value of our 5.25% senior unsecured notes due January 15, 2025 (“2025 Senior Notes”) and 6.625% senior unsecured notes due October 1, 2022 (“2022 Senior Notes”) have been calculated based on quoted prices in active markets and are classified as Level 1. The following table presents a summary of the estimated fair value of our senior notes as of March 31, 2018 and December 31, 2017. March 31, 2018 (in thousands) Level 1 Level 2 Level 3 Total fair value 2025 Senior Notes $ 466,340 $ — $ — $ 466,340 2022 Senior Notes 732,963 — — 732,963 December 31, 2017 (in thousands) Level 1 Level 2 Level 3 Total fair value 2025 Senior Notes $ 464,022 $ — $ — $ 464,022 2022 Senior Notes 734,706 — — 734,706 Nonfinancial Assets and Liabilities Assets and liabilities acquired in business combinations are recorded at their fair value on the date of acquisition. Significant Level 3 assumptions associated with the calculation of future cash flows used in the analysis of fair value of the oil and natural gas property acquired include the Company’s estimate of future commodity prices, production costs, development expenditures, production, risk-adjusted discount rates and other relevant data. Additionally, fair value is used to determine the inception value of the Company’s AROs. The inputs used to determine such fair value are primarily based upon assumptions of the estimated current abandonment costs, discount rate, inflation rate and timing associated with the incurrence of these costs. Our estimated abandonment costs are obtained primarily from independent third parties for costs that would be incurred to restore leased property to the contractually stipulated condition or costs incurred historically for similar work. Additions to the Company’s AROs represent a nonrecurring Level 3 measurement. The Company reviews its proved oil and natural gas properties for impairment purposes by comparing the expected undiscounted future cash flows at a producing field level to the unamortized capitalized cost of the asset. Significant assumptions associated with the calculation of future cash flows used in the impairment analysis include the estimate of future commodity prices, production costs, development expenditures, production, risk-adjusted discount rates and other relevant data. As such, the fair value of oil and natural gas properties used in estimating impairment represents a nonrecurring Level 3 measurement.
Income Taxes	Deferred taxes are determined based on the estimated future tax effects of differences between the financial statement carrying amounts and tax basis of assets and liabilities, given the provisions of enacted tax laws. Tax positions are evaluated for recognition using a more-likely-than-not threshold, and those tax positions requiring recognition are measured as the largest amount of tax benefit that is greater than fifty percent likely of being realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. The Company’s policy is to record interest and penalties relating to uncertain tax positions in income tax expense. We have not recognized any interest and penalties relating to unrecognized tax benefits in our consolidated financial statements.
New Accounting Pronouncements	New Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”). ASU 2016-02 generally requires all lease transactions (with expected lease terms in excess of 12 months) to be recognized on the balance sheet as lease assets and lease liabilities. Public entities are required to apply ASU 2016-02 for annual and interim reporting periods beginning after December 15, 2018 with early adoption permitted. We do not plan to early adopt the standard. We are currently evaluating the impact of ASU 2016-02 on our consolidated financial statements.
Commodity Derivative Instruments	Commodity Derivative Instruments The Company uses derivative instruments to manage its exposure to cash-flow variability from commodity-price risk inherent in its crude oil and natural gas production. The derivative instruments are recorded at fair value on the consolidated balance sheets and any gains and losses are recognized in current period earnings. Our commodity derivatives are comprised of the following instruments: Collars : Each collar transaction has an established price floor and ceiling, and certain collar transactions also include a short put. When the settlement price is below the price floor established by these collars, the Company receives an amount from its counterparty equal to the difference between the settlement price and the price floor multiplied by the hedged contract volume. When the settlement price is above the price ceiling established by these collars, the Company pays its counterparty an amount equal to the difference between the settlement price and the price ceiling multiplied by the hedged contract volume. When the settlement price is below the short put price, the Company receives from its counterparty an amount equal to the difference of the price floor and the short put price multiplied by the hedged contract volume. Swaps : Each swap transaction has an established fixed price. When the settlement price is above the fixed price, the Company pays its counterparty an amount equal to the difference between the settlement price and the fixed price multiplied by the hedged contract volume. When the settlement price is below the fixed price, the counterparty pays the Company an amount equal to the difference between the settlement price and the fixed price multiplied by the hedged contract volume.
Fair Value Measurement	The Company has categorized its assets and liabilities measured at fair value, based on the priority of inputs to the valuation technique, into a three-level fair value hierarchy. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). Assets and liabilities recorded at fair value on the consolidated balance sheets are categorized based on the inputs to the valuation techniques as follows: • Level 1—Assets and liabilities recorded at fair value for which values are based on unadjusted quoted prices for identical assets or liabilities in an active market that management has the ability to access. Active markets are considered to be those in which transactions for the assets or liabilities occur in sufficient frequency and volume to provide pricing information on an ongoing basis. • Level 2—Assets and liabilities recorded at fair value for which values are based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly for substantially the full term of the asset or liability. Substantially all of these inputs are observable in the marketplace throughout the full term of the price risk management instrument and can be derived from observable data or supported by observable levels at which transactions are executed in the marketplace. • Level 3—Assets and liabilities recorded at fair value for which values are based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. Unobservable inputs that are not corroborated by market data and may reflect management's own assumptions about the assumptions a market participant would use in pricing the asset or liability. Valuation techniques that maximize the use of observable inputs are favored. Assets and liabilities are classified in their entirety based on the lowest priority level of input that is significant to the fair value measurement. The assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the placement of assets and liabilities within the levels of the fair value hierarchy.

Summary of Significant Accoun17

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Disaggregation of Revenue	The following table presents our revenues disaggregated by product type and the impact of applying ASC 606 on our current period results: Three Months Ended March 31, 2018 (in thousands) As reported (ASC 606) Historical (ASC 605) Effect of change REVENUES Oil sales $ 251,977 $ 251,977 $ — Natural gas sales 8,432 9,601 (1,169 ) NGLs sales 15,913 18,074 (2,161 ) Total revenues 276,322 279,652 (3,330 ) OPERATING EXPENSES Lease operating expenses 32,135 35,465 (3,330 ) OPERATING INCOME 130,062 130,062 — NET INCOME $ 89,573 $ 89,573 $ —
Schedule of Accounts Receivable	Accounts Receivable (in thousands) As of March 31, 2018 As of December 31, 2017 Sale of oil, natural gas and NGLs $ 110,722 $ 95,942 Joint interest owners 17,141 14,880 Federal income tax receivable 335 335 Total accounts receivable $ 128,198 $ 111,157
Schedule of Oil and Natural Gas Properties	The Company’s oil and natural gas properties as of March 31, 2018 and December 31, 2017 consisted of the following: (in thousands) March 31, 2018 December 31, 2017 Proved oil and natural gas properties $ 4,189,377 $ 3,936,565 Unproved oil and natural gas properties 2,859,631 2,865,952 Total oil and natural gas properties 7,049,008 6,802,517 Less: Accumulated depletion (853,720 ) (778,596 ) Total oil and natural gas properties, net $ 6,195,288 $ 6,023,921
Schedule of Accounts Payable and Accrued Liabilities	Accrued expenses consist of the following: (in thousands) March 31, 2018 December 31, 2017 Accrued capital expenditures $ 91,372 $ 82,748 Other accrued expenses 25,000 36,691 Accrued expenses $ 116,372 $ 119,439
Schedule of Changes in Asset Retirement Obligation	The following is a reconciliation of our ARO liability for the three months ended March 31, 2018: (in thousands) Asset retirement obligation at beginning of period $ 15,849 Liabilities incurred 789 Liabilities settled (278 ) Accretion expense 205 Asset retirement obligation at end of period $ 16,565
Schedule of Income Tax Expense	The following is an analysis of the Company’s consolidated income tax expense for the periods indicated: Three Months Ended March 31, (in thousands) 2018 2017 Current $ — $ 1,498 Deferred 21,932 13,574 Income Tax Expense $ 21,932 $ 15,072

Derivative Instruments (Tables)

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions	The following table summarizes all commodity derivative positions as of March 31, 2018 : Contracts expiring in the period ending: June 30, 2018 September 30, 2018 December 31, 2018 2019 Oil Three-Way Collars: Notional volume (Bbl) 1,941,000 1,319,000 1,227,000 — Weighted average ceiling price ($/Bbl)(1) $ 59.07 $ 60.56 $ 60.96 $ — Weighted average floor price ($/Bbl)(1) $ 47.11 $ 47.79 $ 48.00 $ — Weighted average short put price ($/Bbl)(1) $ 37.11 $ 37.79 $ 38.00 $ — Oil Costless Collars: Notional volume (Bbl) 516,000 1,212,000 1,058,000 2,555,000 Weighted average ceiling price ($/Bbl)(1) $ 60.20 $ 60.10 $ 60.11 $ 58.04 Weighted average floor price ($/Bbl)(1) $ 45.00 $ 46.33 $ 46.52 $ 52.50 Oil Swaps: Notional volume (Bbl) 698,000 322,000 322,000 2,555,000 Weighted average swap price ($/Bbl)(1) $ 62.97 $ 55.77 $ 55.77 $ 55.74 Mid-Cush Differential (Basis) Swaps: Notional volume (Bbl) 2,730,000 2,760,000 2,760,000 2,555,000 Weighted average swap price ($/Bbl)(2) $ (0.42 ) $ (0.42 ) $ (0.42 ) $ (0.29 ) (1) The oil derivative contracts are settled based on the arithmetic average of the closing settlement price for the front month contract NYMEX price of West Texas Intermediate Light Sweet Crude. (2) The Mid-Cush swap contracts are settled based on the difference in the arithmetic average during the calculation period of WTI MIDLAND ARGUS and WTI ARGUS prices in the Argus Americas Crude publication for the relevant period.
Schedule of Fair Value of Derivative Instruments	The following table presents the fair value of our derivative instruments. Our derivatives are presented as separate line items in our consolidated balance sheets as current and noncurrent derivative instrument assets and liabilities based on the expected settlement dates of the instruments. The Company has agreements in place with all of its counterparties that allow for the financial right of offset for derivative assets and derivative liabilities at settlement or in the event of a default under the agreements. However, the fair value amounts are presented on a gross basis in our consolidated balance sheets and do not reflect the netting of asset and liability positions permitted under the terms of the Company’s master netting arrangements. See Note 5 for further discussion related to the fair value of the Company’s derivatives. Assets Liabilities (in thousands) March 31, 2018 December 31, 2017 March 31, 2018 December 31, 2017 Derivative Instruments: Current amounts $ 30,186 $ 64 $ 51,001 $ 36,566 Noncurrent amounts 4,574 37 9,321 5,722 Total derivative instruments $ 34,760 $ 101 $ 60,322 $ 42,288
Derivative Instruments, Gains (Losses)	The following represents the Company’s reported gains on derivative instruments for the periods presented: Three Months Ended March 31, (in thousands) 2018 2017 Net gain on derivative instruments $ 2,907 $ 17,121

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following table presents a summary of the estimated net fair value of our commodity derivative instruments as of March 31, 2018 and December 31, 2017 . (in thousands) Level 1 Level 2 Level 3 Total fair value As of March 31, 2018: Commodity derivative instruments $ — $ (25,562 ) $ — $ (25,562 ) (in thousands) Level 1 Level 2 Level 3 Total fair value As of December 31, 2017: Commodity derivative instruments $ — $ (42,187 ) $ — $ (42,187 ) The following table presents a summary of the estimated fair value of our senior notes as of March 31, 2018 and December 31, 2017. March 31, 2018 (in thousands) Level 1 Level 2 Level 3 Total fair value 2025 Senior Notes $ 466,340 $ — $ — $ 466,340 2022 Senior Notes 732,963 — — 732,963 December 31, 2017 (in thousands) Level 1 Level 2 Level 3 Total fair value 2025 Senior Notes $ 464,022 $ — $ — $ 464,022 2022 Senior Notes 734,706 — — 734,706

Long-Term Debt (Tables)

Long-Term Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of Long-term Debt	Long-term debt consists of the following: (in thousands) March 31, 2018 December 31, 2017 Revolving Credit Facility $ 445,000 $ 375,000 5.25% Senior Notes due 2025 450,000 450,000 6.625% Senior Notes due 2022 700,000 700,000 Less: Discount (900 ) (950 ) Less: Debt issuance costs (14,349 ) (14,922 ) Total long-term debt $ 1,579,751 $ 1,509,128

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Restricted Stock Award Activity	The following table represents restricted stock award activity for the three months ended March 31, 2018: Shares Weighted Average Fair Value Restricted shares outstanding, beginning of period 687,277 $ 32.04 Restricted shares granted 437,608 35.96 Restricted shares canceled (770 ) 30.66 Restricted shares vested (320,001 ) 30.04 Restricted shares outstanding, end of period 804,114 $ 34.97
Schedule of Performance-Based Restricted Stock Award Activity	The following table represents performance-based restricted stock award activity for the three months ended March 31, 2018: Shares Weighted Average Fair Value Restricted shares outstanding, beginning of period 1,001,079 $ 21.14 Restricted shares granted (1) 496,537 23.96 Restricted shares vested (1) (143,824 ) 31.74 Restricted shares outstanding, end of period 1,353,792 $ 21.05

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	A reconciliation of the components of basic and diluted earnings per common share is presented in the table below: Three Months Ended March 31, (in thousands, except per share data) 2018 2017 Numerator: Net income available to stockholders $ 89,573 $ 38,934 Basic net income allocable to participating securities (1) 448 195 Income available to stockholders $ 89,125 $ 38,739 Denominator: Weighted average number of common shares outstanding - basic 157,119 146,054 Effect of dilutive securities: Restricted stock 1,190 951 Weighted average number of common shares outstanding - diluted 158,309 147,005 Net earnings per share: Basic $ 0.57 $ 0.27 Diluted $ 0.57 $ 0.26 (1) Restricted share awards that contain non-forfeitable rights to dividends are participating securities and, therefore, are included in computing earnings using the two-class method. Participating securities, however, do not participate in undistributed net losses.

Nature of Operations and Basi23

Nature of Operations and Basis of Presentation Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
Forecast | RSP, Inc
Business Acquisition [Line Items]
Common stock, par value (in dollars per share)	$ 0.01
Termination fee	$ 250
Concho | Forecast | RSP, Inc
Business Acquisition [Line Items]
Common stock, par value (in dollars per share)	$ 0.001
Consideration transfered, equity interest issued for common shares (in dollars per share)	$ 0.320
Termination fee	$ 350

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Bad debt expense	$ 0	$ 0
Minimum project term to capitalize interest	6 months
Depletion expense	$ 75,400,000	60,400,000
Costs capitalized in connection with exploratory wells in progress	0		$ 0
Impairment of proved oil and gas properties	0	0
Impairment of unproved oil and gas properties	$ 4,200,000	$ 100,000

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Oil sales	$ 251,977	$ 151,637
Natural gas sales	8,432	7,378
NGLs sales	15,913	10,916
Revenues	276,322	169,931
Lease operating expenses	32,135	25,411
Operating Income (Loss)	130,062	55,389
Net income	89,573	$ 38,934
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Oil sales	251,977
Natural gas sales	9,601
NGLs sales	18,074
Revenues	279,652
Lease operating expenses	35,465
Operating Income (Loss)	130,062
Net income	89,573
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Oil sales	0
Natural gas sales	(1,169)
NGLs sales	(2,161)
Revenues	(3,330)
Lease operating expenses	(3,330)
Operating Income (Loss)	0
Net income	$ 0

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Accounts Receivable) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Sale of oil, natural gas liquids and natural gas	$ 110,722	$ 95,942
Joint interest owners	17,141	14,880
Federal income tax receivable	335	335
Total accounts receivable	$ 128,198	$ 111,157

Summary of Significant Accoun27

Summary of Significant Accounting Policies (Oil and Natural Gas) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Oil and Natural Gas Properties [Abstract]
Proved oil and natural gas properties	$ 4,189,377	$ 3,936,565
Unproved oil and natural gas properties	2,859,631	2,865,952
Total oil and natural gas properties	7,049,008	6,802,517
Less: Accumulated depletion	(853,720)	(778,596)
Total oil and natural gas properties, net	$ 6,195,288	$ 6,023,921

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Accrued Expenses) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Accrued capital expenditures	$ 91,372	$ 82,748
Other accrued expenses	25,000	36,691
Accrued expenses	$ 116,372	$ 119,439

Summary of Significant Accoun29

Summary of Significant Accounting Policies (Asset Retirement Obligation) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligation at beginning of period	$ 15,849
Liabilities incurred or assumed	789
Liabilities settled	(278)
Accretion expense	205	$ 153
Asset retirement obligation at end of period	$ 16,565

Summary of Significant Accoun30

Summary of Significant Accounting Policies (Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accounting Policies [Abstract]
Current		$ 1,498
Deferred	$ 21,932	13,574
Income Tax Expense	$ 21,932	$ 15,072

Acquisitions of Oil and Natur31

Acquisitions of Oil and Natural Gas Property Interests - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Delaware Basin
Business Acquisition [Line Items]
Aggregate total purchase price	$ 8.7

Derivative Instruments (Outstan

Derivative Instruments (Outstanding Positions) (Details) - Crude Oil - Forecast	3 Months Ended			12 Months Ended
	Dec. 31, 2018$ / bblbbl	Sep. 30, 2018$ / bblbbl	Jun. 30, 2018$ / bblbbl	Dec. 31, 2019$ / bblbbl
Crude Oil Collars
Derivative [Line Items]
Notional volume (Bbl) | bbl	1,227,000	1,319,000	1,941,000
Weighted average ceiling price (in dollars per Bbl and MMBtu)	60.96	60.56	59.07
Weighted average floor price (in dollars per Bbl and MMBtu)	48	47.79	47.11
Weighted average short put price (in dollars per Bbl)	38	37.79	37.11
Collars Maturing in Next Fiscal Year
Derivative [Line Items]
Notional volume (Bbl) | bbl				0
Weighted average ceiling price (in dollars per Bbl and MMBtu)				0
Weighted average floor price (in dollars per Bbl and MMBtu)				0
Weighted average short put price (in dollars per Bbl)				0
Crude Oil Costless Collars
Derivative [Line Items]
Notional volume (Bbl) | bbl	1,058,000	1,212,000	516,000
Weighted average ceiling price (in dollars per Bbl and MMBtu)	60.11	60.10	60.20
Weighted average floor price (in dollars per Bbl and MMBtu)	46.52	46.33	45
Costless Collars Maturing in Next Fiscal Year
Derivative [Line Items]
Notional volume (Bbl) | bbl				2,555,000
Weighted average ceiling price (in dollars per Bbl and MMBtu)				58.04
Weighted average floor price (in dollars per Bbl and MMBtu)				52.50
Crude Oil Swaps
Derivative [Line Items]
Notional volume (Bbl) | bbl	322,000	322,000	698,000
Weighted average swap price ($/Bbl)	55.77	55.77	62.97
Crude Oil Swaps Maturing In Next Fiscal Year
Derivative [Line Items]
Notional volume (Bbl) | bbl				2,555,000
Weighted average swap price ($/Bbl)				55.74
Mid-Cush Swaps
Derivative [Line Items]
Notional volume (Bbl) | bbl	2,760,000	2,760,000	2,730,000
Weighted average swap price ($/Bbl)	(0.42)	(0.42)	(0.42)
Mid-Cush Swaps Maturing in Next Fiscal Year
Derivative [Line Items]
Notional volume (Bbl) | bbl				2,555,000
Weighted average swap price ($/Bbl)				(0.29)

Derivative Instruments (Gross A

Derivative Instruments (Gross Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Current asset, derivative instruments	$ 30,186	$ 64
Current liability, derivative instruments	51,001	36,566
Noncurrent asset, derivative instruments	4,574	37
Noncurrent liability, derivative instruments	9,321	5,722
Derivative assets	34,760	101
Derivative liabilities	$ 60,322	$ 42,288

Derivative Instruments (Gain Lo

Derivative Instruments (Gain Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Net gain on derivative instruments	$ 2,907	$ 17,121

Derivative Instruments (Narrati

Derivative Instruments (Narrative) (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Collateral posted for derivative instruments with credit-risk related contingent features	$ 0	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of the Extimated Fair Value of Senior Notes (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Aug. 10, 2015
Senior Notes | 2025 Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.25%
Long-term debt, fair value	$ 466,340	$ 464,022
Senior Notes | 2025 Senior Notes | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	466,340	464,022
Senior Notes | 2025 Senior Notes | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	0	0
Senior Notes | 2025 Senior Notes | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	0	0
Senior Notes | 2022 Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	732,963	734,706
Senior Notes | 2022 Senior Notes | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	732,963	734,706
Senior Notes | 2022 Senior Notes | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	0	0
Senior Notes | 2022 Senior Notes | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 0	$ 0
Senior Unsecured Notes | 6.625% Notes due 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.625%		6.625%

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value Measurements - Fair Value Hierarchy on a Recurring Basis (Details) - Recurring basis - Commodity derivative instruments - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets (liabilities)	$ (25,562)	$ (42,187)
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets (liabilities)	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets (liabilities)	(25,562)	(42,187)
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets (liabilities)	$ 0	$ 0

Long-Term Debt (Schedule of Lon

Long-Term Debt (Schedule of Long-term Debt) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Less: Discount	$ (900)	$ (950)
Less: Debt issuance costs	(14,349)	(14,922)
Total long-term debt	1,579,751	1,509,128
2025 Senior Notes | Senior Notes
Debt Instrument [Line Items]
Long term debt	450,000	450,000
6.625% Notes due 2022 | Senior Unsecured Notes
Debt Instrument [Line Items]
Long term debt	700,000	700,000
Revolving credit facility | Line of Credit
Debt Instrument [Line Items]
Long term debt	$ 445,000	$ 375,000

Long-Term Debt (Narrative) (Det

Long-Term Debt (Narrative) (Details)	Dec. 27, 2016USD ($)	Mar. 31, 2018USD ($)financial_ratio	Dec. 31, 2016	Dec. 31, 2017USD ($)	Aug. 10, 2015USD ($)	Sep. 26, 2014USD ($)
Debt Instrument [Line Items]
Letters of credit outstanding, amount		$ 1,900,000
Senior Notes | 2025 Senior Notes
Debt Instrument [Line Items]
Long term debt		$ 450,000,000		$ 450,000,000
Debt issued, face amount	$ 450,000,000
Stated interest rate		5.25%
Senior Notes | 2025 Senior Notes | January 15, 2020
Debt Instrument [Line Items]
Percentage of original principal amount of debt at which debt can be redeemed	103.938%
Senior Notes | 2025 Senior Notes | January 1, 2023
Debt Instrument [Line Items]
Percentage of original principal amount of debt at which debt can be redeemed	100.00%
Senior Notes | 2025 Senior Notes | Prior To January 15, 2020
Debt Instrument [Line Items]
Percentage of original principal amount of debt at which debt can be redeemed			100.00%
Senior Unsecured Notes | 2025 Senior Notes | Event of change in control
Debt Instrument [Line Items]
Percentage of original principal amount of debt at which debt can be redeemed	101.00%
Senior Unsecured Notes | 6.625% Notes due 2022
Debt Instrument [Line Items]
Long term debt		$ 700,000,000		700,000,000
Debt issued, face amount					$ 200,000,000	$ 500,000,000
Stated interest rate		6.625%			6.625%
Percentage of principal amount issued					99.25%
Senior Unsecured Notes | 6.625% Notes due 2022 | After October 1, 2017
Debt Instrument [Line Items]
Percentage of original principal amount of debt at which debt can be redeemed		104.969%
Senior Unsecured Notes | 6.625% Notes due 2022 | January 1, 2020
Debt Instrument [Line Items]
Percentage of original principal amount of debt at which debt can be redeemed		100.00%
Senior Unsecured Notes | 6.625% Notes due 2022 | Event of change in control
Debt Instrument [Line Items]
Percentage of original principal amount of debt at which debt can be redeemed		101.00%
Revolving credit facility
Debt Instrument [Line Items]
Line of credit, maximum borrowing capacity		$ 1,500,000,000
Line of credit facility, maximum borrowing capacity, elected commitment		900,000,000
Credit agreement, maximum borrowing capacity, lender commitments		$ 2,500,000,000
Number of financial ratios | financial_ratio		2
Working capital ratio, required		1
Leverage ratio, required		4.25
Weighted average interest rate		3.90%
Credit agreement, remaining borrowing capacity		$ 453,100,000
Revolving credit facility | Line of Credit
Debt Instrument [Line Items]
Long term debt		$ 445,000,000		$ 375,000,000
Revolving credit facility | Eurodollar
Debt Instrument [Line Items]
Variable rate basis, base percentage prior to adjustments		100.00%
Revolving credit facility | Eurodollar | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		1.50%
Line of credit facility, unused capacity, commitment fee percentage		0.375%
Revolving credit facility | Eurodollar | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		2.50%
Line of credit facility, unused capacity, commitment fee percentage		0.50%
Revolving credit facility | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate		0.50%
Revolving credit facility | Adjusted LIBOR rate
Debt Instrument [Line Items]
Basis spread on variable rate		1.00%
Revolving credit facility | Adjusted LIBOR rate | Minimum
Debt Instrument [Line Items]
Interest rate terms, percentage of borrowing base utilized margin		0.50%
Revolving credit facility | Adjusted LIBOR rate | Maximum
Debt Instrument [Line Items]
Interest rate terms, percentage of borrowing base utilized margin		1.50%

Equity-Based Compensation (Narr

Equity-Based Compensation (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Feb. 28, 2018	Mar. 31, 2018	Mar. 31, 2017
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense		$ 26.3
Unrecognized compensation expense, weighted average recognition period		2 years 2 months
Performance-based restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense		$ 19.4
Unrecognized compensation expense, weighted average recognition period		1 year 9 months 18 days
Stock awards granted during the period (in shares)		496,537
Target payout percentage		100.00%
Performance-based restricted stock awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target payout percentage		0.00%
Performance-based restricted stock awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target payout percentage		200.00%
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation		$ 5.3	$ 3.9
Awards In 2018 | Performance-based restricted stock awards | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target payout percentage	0.00%
Awards In 2018 | Performance-based restricted stock awards | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Target payout percentage	100.00%

Equity-Based Compensation (Sche

Equity-Based Compensation (Schedule of Restricted Stock Award Activity) (Details) - Restricted stock awards	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Shares (in shares)
Restricted shares outstanding, beginning of period (in shares) | shares	687,277
Restricted shares granted (in shares) | shares	437,608
Restricted shares canceled (in shares) | shares	(770)
Restricted shares vested (in shares) | shares	(320,001)
Restricted shares outstanding, end of period (in shares) | shares	804,114
Weighted Average Fair Value (in dollars per share)
Restricted shares outstanding, beginning of period (in dollars per share) | $ / shares	$ 32.04
Restricted shares granted (in dollars per share) | $ / shares	35.96
Restricted shares canceled (in dollars per share) | $ / shares	30.66
Restricted shares vested (in dollars per share) | $ / shares	30.04
Restricted shares outstanding, end of period (in dollars per share) | $ / shares	$ 34.97

Equity-Based Compensation (Sc42

Equity-Based Compensation (Schedule of Performance-Based Restricted Stock Award Activity) (Details) - Performance-based restricted stock awards	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards granted during the period (in shares) | shares	496,537
Shares (in shares)
Restricted shares outstanding, beginning of period (in shares) | shares	1,001,079
Restricted shares vested (in shares) | shares	(143,824)
Restricted shares outstanding, end of period (in shares) | shares	1,353,792
Weighted Average Fair Value (in dollars per share)
Restricted shares outstanding, beginning of period (in dollars per share) | $ / shares	$ 21.14
Restricted shares granted (in dollars per share) | $ / shares	23.96
Restricted shares vested (in dollars per share) | $ / shares	31.74
Restricted shares outstanding, end of period (in dollars per share) | $ / shares	$ 21.05

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income	$ 89,573	$ 38,934
Basic net income allocable to participating securities	448	195
Income (loss) available to stockholders	$ 89,125	$ 38,739
Denominator:
Weighted average number of common shares outstanding - basic (in shares)	157,119	146,054
Effect of dilutive securities:
Restricted stock (in shares)	1,190	951
Weighted average number of common shares outstanding - diluted (in shares)	158,309	147,005
Net income (loss) per share:
Basic (in dollars per share)	$ 0.57	$ 0.27
Diluted (in dollars per share)	$ 0.57	$ 0.26